E0166 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0166.rs

Error E0166 needs a span_label, updating it from:

error[E0166]: `return` in a function declared as diverging
  --> src/test/compile-fail/E0166.rs:11:17
   |
11 | fn foo() -> ! { return; } //~ ERROR E0166
   |                 ^^^^^^

To:

error[E0166]: `return` in a function declared as diverging
  --> src/test/compile-fail/E0166.rs:11:17
   |
11 | fn foo() -> ! { return; } //~ ERROR E0166
   |                 ^^^^^^ diverging function cannot return

[Roybie]

Taking this one